\begin{sloppypar} 
The approach followed for the creation of a LOD dataset
from FrameNet\footnote{\small{The dataset can be accessed through the SPARQL endpoint at http://bit.ly/fnsparql, as framenet\_dataset}} is both derived from the transformation method implemented by
Semion~\cite{Semion} and based on an iterative evaluation of the quality of
the output produced with respect to the semantics of FrameNet formalized into
a ``gold standard''
ontology\footnote{\small{http://ontologydesignpatterns.org/cp/owl/fn/framenet.owl}} that we have used for the evaluation. 
% Semion is a ``triplifier'' that implements a transformation process into two
% steps:
% \begin{itemize}
%   \item a \textbf{syntactic transformation} from the original format of the data
%   source to RDF datasets, according to an OWL ontology that represents the data
%   source structure: the source meta-model.
%   \item a \textbf{refactoring} step that allows to transform the obtained RDF
%   dataset through to a set of rules defined according to SemionRules,
%   a rule language that wraps around SPARQL Construct and
%   Update, adding some additional features such as forward chaining and
%   renaming facilities.
% \end{itemize} 
Based on that, the transformation of FrameNet v.1.5 from XML to RDF
consisted into two steps: (i) the syntactic transformation of the XML source to RDF
according to the OWL meta-model that describes the structure of the
source\footnote{\small{http://www.ontologydesignpatterns.org/ont/iks/oxml.owl}}, (ii)
the design and the application of a refactoring recipe for the ABox refactoring
on the RDF produced in the first step. The recipe was derived generalizing and
revising some of the common transformation practices from existing tools (i.e.
XML2OWL~\cite{bohring-2005}, TopBraid
Composer\footnote{\small{http://www.topbraidcomposer.com}}, Rhizomik
ReDeFer~\cite{rhizomik}). For example we used the following mappings:
% Before starting with the ABox refactoring, we produced
% the syntactic reengineering of the original FrameNet XML version 1.5 to RDF. Semion needs a meta-model that describes the
% structure of the original source, and we used the default OWL meta-model for
% XML sources provided by the tool\footnote{http://www.ontologydesignpatterns.org/ont/iks/oxml.owl}.
% After that, we have analyzed some existing tools (i.e. XML2OWL~\cite{bohring-2005},
% TopBraid Composer\footnote{http://www.topbraidcomposer.com}, Rhizomik ReDeFer~\cite{rhizomik}) able to
% transform XML to RDF, in order to extract and 
% generalize a common refactoring recipe for Semion from the best existing practices.
% Approaches to the transformation adopted by those tools, despite notable
% differences, are quite homogeneous in terms of the output produced. 
%The generalization of a recipe derived from this analysis can be summarized as
%follows: 
(i) a \texttt{xsd:ComplexType} is mapped to an \texttt{owl:Class},
(ii) a \texttt{xsd:SimpleType} is mapped to an \texttt{owl:DatatypeProperty}
and (iii) a \texttt{xsd:Element} is mapped either to
an \texttt{owl:ObjectProperty} or to a \texttt{owl:DatatypeProperty}. 
Further details can be found in~\cite{bohring-2005}.
\end{sloppypar}
As an example, according to the syntax of the rules for the Semion
refactoring, we have that the mapping (i) is expressed as
\begin{verbatim}
is(oxsd:ComplexType, ?type) 
    -> 
is(owl:Class, ?classNode) 
\end{verbatim}	 
and maps any individual of the class \emph{oxsd:ComplexType} to a
\emph{owl:Class}.
% \begin{verbatim}
% is(oxsd:Element, ?elem) . 
% has(oxsd:hasType, ?elem, ?type) .
% is(oxsd:ComplexType, ?type)
%    ->
% is(owl:ObjectProperty, ?elem)
% \end{verbatim}
% that maps an element declaration of the schema that is declared with a complex
% type to an \emph{owl:ObjectProperty}.\newline
We refer to the Semion wiki\footnote{\small{http://stlab.istc.cnr.it/stlab/Semion}}
for more information about the tool and the syntax of the rules.\newline
The relavance of a syntanctic transformation and a following refactoring can
be clarified saying that it is designed as a semi-automatic approach which
allows, via the refactoring rules, for better addressing the
domain semantics of the original source.
% Although this sort of mapping recipe from XML to OWL can be
% considered well accepted and used, it does not provide a substantial method
% for the extraction of the domain semantics from a structured, but non-relational format
% like XML. 
As an example, we can consider a simple frame-to-frame relation like\newline
%$$
\texttt{Inherits\_from(Abounding\_with,\mbox{ }Locative\_relation)}\newline
%$$
which expresses the fact that the frame \textit{Abounding\_with} inherits the
schematic representation of a situation involving various participants, properties, and
other conceptual roles from the frame \textit{Locative\_relation}. This relation
is expressed in the XML FrameNet notation as:
\begin{verbatim}
<frame name="Abounding_with" ... ID="262">
  ...
  <frameRelation type="Inherits from">
    <relatedFrame>
      Locative_relation
    </relatedFrame>
  </frameRelation>
  ...
</frame>
\end{verbatim}
and, with most of the existing tools, it is transformed to the RDF schematized
in Figure \ref{commonRecipe}.  It is easy to notice how the
\texttt{Inherits from} frame-to-frame relation is realized through the
reification of the relation \texttt{RelatedFrame\_i}, that expresses its type
and the related frames, i.e.
\texttt{Inherits from} and \texttt{Locative\_relation}, as literals.
\begin{figure}[h!]
\centering
	\includegraphics[scale=0.18]{img/exampleXML.png}
	\caption{The ``Inherits from'' relation
	mapped to RDF with a common transformation recipe.}\label{commonRecipe}
\end{figure}
\newline Instead, adopting the syntactic transformation of
Semion, we have produced firstly an RDF graph, which is depicted in Figure~\ref{reengineering}\footnote{\small{\texttt{oxsd}}
and \texttt{oxml} are the default ontologies of Semion for XSD and XML data structures.}.
\begin{figure}[h!]
\centering
	\includegraphics[scale=0.18]{img/reengineer.png}
	\caption{Example of reengineering of the frame
	``Abounding with'' with its XSD definition.}\label{reengineering}
\end{figure} 
\begin{sloppypar}
In the figure, \textit{fntbox:Frame} is no longer an \textit{owl:Class},
but an \textit{oxsd:Element} and \textit{fnabox:Abounding\_with} is an
\textit{oxml:XMLElement} related to \textit{fntbox:Frame} through
\textit{oxsd:hasElementDeclaration}.
\end{sloppypar}
After having was syntactically converted  FrameNet from XML to RDF, we applied
the general recipe with the Semion Refactorer, in order to derive a LOD dataset for FrameNet.
As the recipe is based on a general conversion from XML to OWL, the result was
far from being a good formalization of the semantics of FrameNet. For that
reason, we have incrementally refined the recipe in order to fill the gap
between the semantics expressed by the output produced by the refactoring and
the gold standard we had previously defined.
%******** REVIEW ***************
% ISSUE 8
% Block added by Andrea
We remark that the aim of the refactoring is to transform one RDF source to
another trying to preserve either explicit or implicit domain
semantics of the original source without information loss.
% End of block
\newline 
For example, the rule which allows to avoid the reification of
frame-to-frame relations is shown in Figure \ref{reificationRule}.
\begin{figure}[h!]
\centering
	\includegraphics[scale=0.28]{img/reificationRuleBW.png}
	\caption{Rule which allows to express frame-to-frame
	relation as binary relations.}\label{reificationRule}
\end{figure}
% \begin{verbatim}
% ... 
% values(oxml:nodeValue, ?xmlAttr, ?value) . 
% values(oxml:nodeName, ?xmlAttr, 
%        "type"^^xsd:string) . 
% has(composite:child, ?xmlElem, ?child) . 
% values(oxml:nodeValue, ?child, ?childValue) . 
% let(?relatioURI, concat(namespace(?frame), 
%                         trim(?value)
% ) .
% let(?frameURI, concat(namespace(?frame), 
%                         concat("frame/",
%                                ?childValue
%                         )
%                )
% ) . 
%  
% newNode(?frameRelation, ?frameURI) . 
% newNode(?relatedFrame, ?frameURI)
% 
%    ->
%    
% is(owl:ObjectProperty, ?frameRelation) .  
% has(rdfs:subPropertyOf, ?frameRelation, 
%     fns:hasFrameRelation) . 
% has(?frameRelation, ?frame, ?relatedFrame) .
% \end{verbatim}
The rule shown in Figure \ref{reificationRule} transforms all the frame-to-frame
relations into binary relations between frames. The rule extracts the type of
the relation from the \texttt{nodeValue} associated with the \texttt{type} attribute of a frame. Then it
creates a new object property as a sub-property of \texttt{hasFrameRelation}, and resolves
the name of the related frame that is expressed as a literal in the
\texttt{relatedFrame} element, as shown in the XML code before. We remark that the
model accessed by rules is not anymore the original XML source, but its syntactic
translation to RDF. Figure \ref{frame2frame} shows the RDF of the
\texttt{inherits from} relation between the frames \texttt{Abounding with} and
\texttt{Locative relation} obtained by applying the refactoring recipe with Semion.
\begin{figure}[h!]
\centering
	\includegraphics[scale=0.18]{img/frame2frame.png}
	\caption{The ``Inherits from'' frame-to-frame relation
	between the frames ``Abounding with'' and ``Locative
	relation'' after the refactoring.}\label{frame2frame}
\end{figure}
Figure \ref{schema} shows the core fragment of the OWL schema of
FrameNet used as a vocabulary for the data from FrameNet.
\begin{figure}[h!]
\centering
	\includegraphics[scale=0.06]{img/framenetSchema.png}
	\caption{A fragment of the FrameNet OWL schema.}\label{schema}
\end{figure}
\newline
%******** REVIEW ***************
% ISSUE 6
% Block added by Andrea 
The complete refactoring recipe\footnote{\small{http://stlab.istc.cnr.it/stlab/FrameNetKCAP2011\#
tab=ABoxRefactoring}} is composed by 58 transformation
rules in forward-chaining inference mode.
% End of block 
% More details about the refactoring recipe and the rule language used can be found in the Frame LOD
% wiki.
\newline
An important feature of FrameNet as a dataset in the LOD cloud 
%******** REVIEW ***************
% ISSUE 13
% Block added by Andrea
, that will be investigated as part of our ongoing work, 
% End of block 
is the mapping of its frames and frame
elements to other lexical resources, e.g. WordNet. WordNet is available as a LOD dataset since 2006 as a result of the W3C working draft~\cite{Schreiber:06:RRW}. Such mappings can be obtained from VerbNet~\cite{KipperSchuler2006}, a
lexical resource that incorporates both semantic and syntactic information about
English verb semantics. The VerbNet 3.1 XML database provides mappings between VerbNet classes, FrameNet frames, and WordNet synsets.\newline
%\begin{verbatim}
%as it can be seen in XML below:
%...
%<MEMBER name="accompany" 
%   wn="accompany%2:38:00 ?accompany%2:42:01"
%   grouping="accompany.01"/>
%... 
%<vncls class='51.7' vnmember='accompany' 
%   fnframe='Cotheme' fnlexent='965'
%   versionID='vn1.5' />
%...
%\end{verbatim}
For example, from the VerbNet mappings converted to RDF:\footnote{\small{prefixes:
skos: http://www.w3.org/2004/02/skos/core\#; vnclass: http://www.ontologydesignpatterns.org/ont/vn/class/; wndata: http://www.w3.org/2006/03/wn/wn20/instances/; frame: http://www.ontologydesignpatterns.org/ont/framenet/ frame/}}\newline \texttt{
vnclass:accompany skos:exactMatch\\
wndata:synset-accompany-verb-2
}\newline\newline
\texttt{
vnclass:accompany \texttt{skos:exactMatch}\\
frame:Cotheme
}\newline\newline
%By transitivity of \texttt{skos:exactMatch} we also obtain: \newline\newline
%\texttt{
%wndata:synset-accompany-verb-2 \\
%skos:exactMatch frame:Cotheme
%}\newline\newline
%The XML sample from VerbNet maps the member \textit{accompany}:
%\begin{itemize}
%  \item to the WordNet synset \textit{accompany\_2}
%  \item to the FrameNet frame \textit{Cotheme} 
%\end{itemize}
%
The VerbNet dataset
%\footnote{\small{http://www.ontologydesignpatterns.org/ont/vn/}}
excerpt is intended to demonstrate linkings between lexical
resources. An official release will be published in the near future.